Project Summary: A principle aim of the NIDCD is the study of the sensorimotor processing in normal and disordered communication. However, the specific mechanisms which mediate vocal communication are poorly understood. In this proposal, I directly address these issues using the songbird (zebra finch) as a model system. The proposal focuses on the high vocal center (or HVC), which is a forebrain structure analygous to motor cortex in humans. A number of methods will be applied to the study of HVC, with the goal of elucidating cellular and synaptic rules that govern the function Of that nucleus in order to better understand its function and to ultimately shed light into disorders in human communication. The first specific aim will address the importance of HVG in providing the song system with timing information. In preliminary studies, I have used a thermoelectric device to alter the temperature of HVC in the singing zebra finch, which results in a modification of song duration. Cooling HVC leads to slower singing; heating HVC speeds the song. 1 will extend these studies Into RA (the downstream target of HVC) in order to directly test whether HVC acts as an autonomous clock within the song system. The second specific aim will address the cellular mechanisms that contribute to pattern generation within HVG. The proposed experiments will elucidate the cellular and/or synaptic mechanisms that terminate HVC bursts, leading to sparse, feature-selective neuronal activity within that nucleus. The third specific aim will address the circuit mechanisms that contribute to pattern generation within HVC. Almostnothing is known about the rules that govern HVC synaptic connections. 1 will record from pairs of HVC cells to study the static and dynamic properties governing HVC synapses. These experiments will allow for a better understanding of the functional principles and topographic organization of HVC.